Various devices are known and available to assist rifle users in accurately hitting a target, such as at a rifle shooting range or in other shooting environments. These known targeting aid devices run the gamut from complex computerized devices to simple traditional flash cards and other visual aids, such as those incorporating a “Mildot” Scale.
One known computer-based targeting aid is disclosed in U.S. Pat. No. 5,194,006 of Zaenglein, which describes a complex type of rifle sighting and aiming device, using a computer.
U.S. Pat. No. 6,196,455 of Robinson discloses a range and drop calculator for use with telescopic gun sights. While the scale on Mr. Robinson's calculator is useful for adjusting the actual line of sight distance, line of sight distancing in practice is not the most accurate. For that matter, the scale is smaller in range.
Also, while simple devices based in the “Mildot” scale may be used for measurement reference when looking at a target through a scope, this simple scale is not broken down fine enough for 10ths of a mil so is not effective in some application. That is, devices using the “Mildot” scale may be OK for short distance calculation that do not need that fine of a breakdown, but at 800 yards+ a target size of 5′10″ measures 2.1 vs. 2.25 in mils, which makes a big difference to the accuracy of the answer. At that range, an incorrect distance to target by 5-10% will result in a miss because the bullet is falling more rapidly. In addition, the “Mildot” scale is not spaced out evenly, to accurately let the operator fudge it a little.
Robinson '455 cannot use any other range finding recticle other than “Mildot,” so it cannot be used or issued universally as a primary or a backup device. This is because the scale used by Robinson is specialized for only “Mildot.” Moreover, the Robinson '455 calculator cannot mix units of measure within a formula, nor add or subtract, multiply or divide, perform windage calculations or target lead calculations. While Robinson '455 can calculate hold off's/Kentucky windage, which is used when there is no time for actual scope adjustments and actually championed by some rather than physical adjustments, the Robinson '455 calculator cannot accurately perform such calculations where the user does not have the exact chart in the his/her possession. Almost all of the information needed for long distance shooting (except how to take several different wind speeds and directions) can be had on various charts because there is no magic. It just becomes a tremendous amount of information for a user to maintain control of, requiring the user to rely upon handheld calculators or PDA's.
Robinson '455 makes many references to ease of use and the fact that having the formula's “built into the scales” (while perhaps limiting usefulness to “Mildot” reticles), which makes Robinson's calculator faster to use. However, ease of use is only useful when it completes the total process needed for the job at hand. If one still needs scrap paper or other calculator devices to perform the total process, the ease of use in Robinson '455 is actually negated because there is a need for several more components to be carried and mastered, even though it might only be a calculator. Picking up one for half of the process, putting it down with the information still visible then picking up another device and transposing the info becomes a lot harder all of a sudden. And of course these additional steps increase the likelihood errors will occur by use of multiple devices simultaneously.
Additionally, when sighting a target with a rifle scope, the elevation adjustment/bullet drop of a projectile is not a perfect curve or semi circle. It is more like a home run in base ball, the projectile starts out fast and straight as it moves away from the gun barrel, but towards the end of the trajectory the forward movement slows considerably as it drops more quickly. Using the Robinson '455 device, the user is only “moving” the point on the curve and then taking an answer. A more accurate way is to find the adjustment at the original distance and then take the cosine of said adjustment, which is called “modified rifleman's rule”. The most accurate angle adjustment is called the “slope offset method.” But to perform or utilize an accurate adjustment formula requires addition, subtraction, multiplication and division, all of which are not able to be performed on Robinson '455's device.
Furthermore, in a typical example of rifle target sighting, there is a difference of about 0.5 MOA (4″) at 800 yards for any particular cartridge. A quality rifle at that range should be able to keep most bullets within an 8 inch circle at that particular distance. This suggested accuracy, however, is without the added consideration of environmental factors, such as wind direction and speed, and air temperature. So, if a sniper is going for a head shot of a simulated insurgent firing on troops, but the simulated target is only showing his head in the window of the target (a head is approx 10×8 inches), the sniper has only 1 inch above the target and 1 inch below (theoretical circle of accuracy) where he aims at the nose of the head of the simulated insurgent portrayed on the target. Add in 4 inches of improper elevation adjustment and the bullet will sail several inches over the head of the simulated insurgent on the window of the target.